EP 0 240 023 B1 discloses an optoelectronic arrangement which is capable of detecting relative linear movement or relative positions along axes of a Cartesian coordinate system, as well as rotational movement about these axes. To this end, six light-emitting elements spaced at identical angular distances from one another are disposed within a plastic ball. A stationary slit diaphragm is disposed in front of each light-emitting element. Relative movements and relative positions are detected by light-sensitive detectors arranged so, as to be movable with respect to the light-emitting elements and slit diaphragms.
From DE 100 34 569 A1 a device for detecting relative movement of two objects is known which employs an optoelectronic arrangement as disclosed in EP 0 240 023 B1. The device is particularly suited for industrial applications where high forces and torque occur. For this purpose, the detection device is provided, between an inlet and outlet flange, with an intermediate member made from an elastomer or cast resin in addition to an arrangement of helical springs. In this way, the device can accommodate particularly high forces and torque.
Further, DE 36 11 336 C2 discloses a force and torque sensor which measures all six possible force and torque components in a Cartesian coordinate system by means of strain gauges. The apparatus consists of two spoked wheels arranged above one another with four spokes each and a total of twenty mutually wired strain gauges.
Conventional sensors such as above exhibit a drawback in that their measurement range is limited. If the sensor is loaded beyond this measurement range, damage may occur to the sensor. In the sensor of EP 0 240 023 B1, for example, the light-sensitive detectors may come in contact with the light-emitting elements or the slit diaphragms upon too large a deflection and thus bring the whole arrangement out of adjustment or render it entirely useless. In the sensor of DE 36 11 336 C2, overstretching of the strain gauges or failure of the spokes may occur.
Generally, it can not be ensured that the extent of relative movement of two objects is always smaller than the measurement range of the sensor. In fact, in numerous applications, it may occur from time to time that the measurement range of the sensor is exceeded. Then, it may become necessary to replace the sensor with a new one if the old one is destroyed or becomes maladjusted or inoperative due to an excessive relative displacement of the objects, in order to ensure that subsequent measurements are reliable and correct. The replacement of a sensor is often cumbersome and involves immediate costs. Additionally, if the sensor plays a central role in, e.g., a production facility and production has, to be halted until the sensor is replaced, considerable secondary costs may occur.
Thus, there is a desire for a position and/or movement sensor that is less susceptible to damage or mal-function if the measurement range of the sensor is exceeded. There is also a desire for a force and/or torque sensor that is likewise less susceptible to such damage or mal-function.